re: Measuring trees for Louisiana/National big tree registry

Yep, pretty sure. Its only been in the last 20 years that every parcel of land has been posted. And botanists know which lands to look on. If you look at the taxo-visited sites by parish at the big herbariums (the ones that are finished) you see the suckers covered with hundreds, sometimes thousands of sites. But,obviously there may be a very very few trees that are old enough to be near records and haven't been seen by a forester, taxo botanist, botanist, amateur reporters, etc., but I doubt it.
I remember being with a taxo professor that was doing a friend of a friend a favor and checked out an oak tree (dont remember the species)whilein the area. After looking at it, he told the owner it was "very impressive" etc, but it wasnt nearly a record. the owner asked how much bigger it had to get....the professor said - "about twice that size".